Grain size inspection of a gas turbine component by x-ray refraction

Abstract

A system and method for inspecting a grain size of a cast alloy component while maintaining the structural integrity of the cast alloy component is disclosed. The method includes recording a radiographic image of the component, identifying areas of the component to be inspected, and locating one or more lines having a pre-determined length on the radiographic image at an area to be inspected. Then, a total number of intersections with the one or more lines are determined and an average grain size is calculated.

What is claimed is: 
     
         1 . A method of inspecting a grain size of a cast alloy component while maintaining the structural integrity of the cast alloy component comprising:
 recording a radiographic image of the component;   identifying areas of the component to be inspected;   locating one or more lines having a pre-determined length on the radiographic image at one of the areas to be inspected;   calculating a total number of intersections of grain boundaries with the one or more lines; and   calculating an average grain size.   
     
     
         2 . The method of  claim 1 , wherein the cast alloy component is a turbine blade or turbine vane. 
     
     
         3 . The method of  claim 2 , wherein the cast alloy component is cast with an equiax grain or directionally-solidified structure. 
     
     
         4 . The method of  claim 3 , wherein the areas of the cast alloy component to be inspected are located along an airfoil. 
     
     
         5 . The method of  claim 4 , wherein the areas to be inspected along the airfoil are spaced at different radial locations. 
     
     
         6 . The method of  claim 1 , wherein the pre-determined length of the one or more lines is approximately 0.5 inches. 
     
     
         7 . The method of  claim 1 , wherein the average grain size is calculated based on the ratio of the length of the line to number of intersections. 
     
     
         8 . The method of  claim 2 , wherein multiple lines are located within a single radial section of the airfoil. 
     
     
         9 . The method of  claim 1 , wherein the method is capable of identifying a chill grain as small as 0.020″ in the cast alloy component. 
     
     
         10 . The method of  claim 1 , wherein calculating the number of intersections is determined by an operator upon visual inspection of the radiographic image. 
     
     
         11 . The method of  claim 1 , wherein the areas of the component to be inspected are determined by an operator. 
     
     
         12 . A non-destructive radiographic inspection technique for determining a grain size of a gas turbine casting comprising:
 identifying inspection areas from a radiographic image of the casting;   locating one or more lines having a pre-determined length on the radiographic image at a radial orientation on the casting; and,   determining a total number of intersections of grain boundaries with the one or more lines;   wherein an average grain size is calculated based on the ratio of line length to total number of intersections.   
     
     
         13 . The inspection technique of  claim 12 , wherein the inspection areas are located generally along an airfoil portion of the turbine casting. 
     
     
         14 . The inspection technique of  claim 12 , wherein the one or more lines extend a length of approximately 0.5 inches. 
     
     
         15 . The inspection technique of  claim 12 , wherein determining the total number of intersections of grain boundaries with the one or more lines is made by an operator. 
     
     
         16 . The inspection technique of  claim 12 , wherein the cast alloy is an equiax casting. 
     
     
         17 . A computer readable media for determining a grain size of a cast turbine component comprising:
 recording a radiographic image of the component;   identifying areas of the component to be inspected;   locating one or more lines having a pre-determined length on the x-ray image at one of the areas to be inspected;   calculating a total number of intersections of grain boundaries with the one or more lines; and   calculating an average grain size.   
     
     
         18 . The computer-readable media of  claim 17 , wherein calculating the average grain size is calculated based on a ratio of line length to total number of intersections. 
     
     
         19 . The computer-readable media of  claim 17 , wherein the inspection areas are located generally along an airfoil portion of a turbine casting. 
     
     
         20 . The computer-readable media of  claim 17 , wherein calculating the total number of intersections of grain boundaries with the one or more lines requires input from an operator.